Dermatologists recognize many different types of hair loss, the most common being “alopecia” or “baldness” wherein humans (mostly males) begin losing scalp hair at the temples and on the crown of their head. However, hair loss may be due to many other disorders.
Hair loss is often accompanied by a change in the hair growth cycle. All mammalian hair passes through a life cycle that includes the anagen phase, the catagen phase and the telogen phase. The anagen phase is the period of active hair growth. In the scalp, this phase lasts from 3-5 years. The catagen phase is a short 1-2 week transitional phase between the anagen phase and the telogen phase. The final telogen phase is considered a “resting phase” where all growth ceases. This phase is also relatively short-lived lasting about 3-4 months before the hair is shed and a new one begins to grow. With the onset of baldness, a successively greater proportion of hairs are in the telogen phase with correspondingly fewer in the active growth anagen phase.
Additionally, different types of hair exist including terminal hairs, vellus hairs and modified terminal hairs. Terminal hairs are coarse, pigmented, long hairs in which the bulb of the hair follicle is seated deep in the dermis. Vellus hairs, on the other hand, are fine, thin, non-pigmented short hairs in which the hair bulb is located superficially in the dermis. Modified terminal hairs are seen in eye lashes and eye brows. As alopecia progresses, a transition takes place wherein the hairs themselves change from the terminal to the vellus type. Accordingly, alopecia (baldness) also includes a deficiency in terminal hairs.
One non-drug treatment for alopecia is hair transplantation. Plugs of skin containing hair are transplanted from areas of the scalp where hair is growing to bald areas. This approach can be reasonably successful, however it is costly, time-consuming and painful. Other non-drug related approaches to treating alopecia include ultra-violet radiation, massage, psychiatric treatment and exercise therapy. None of these approaches, however, have been generally accepted as effective. Even such things as revascularization surgery or acupuncture have shown little, if any, effect.